Aquarium filter



FIG. 1 is a perspective view of an aquarium filter, showing my new design;

FIG. 2 is a top plan view;

FIG. 3 is a left rear elevational view, the right rear being a mirror image thereof;

FIG. 4 is an elevational view taken from the left front and left rear thereof;

FIG. 5 is a left front elevational view, the right front being a mirror image thereof;

FIG. 6 is an elevational view taken from left front and right front thereof; and

FIG. 7 is a bottom plan view. 

The ornamental design for an aquarium filter, substantially as shown and described. 